Relationship between the shift of socioeconomic status and cardiovascular mortality

Abstract

Background The aim of this study is to investigate whether upward or downward shifts in socioeconomic status have an effect on cardiovascular mortality. Design A retrospective cohort study. Methods Among the Korean National Health Insurance Service National Sample Cohort, 178,812 subjects were selected who were over 20 years of age as of 2002, with available data on routine health check and free of a diagnosis of ischaemic heart disease, stroke, heart failure or cancer at baseline. Cause of death was identified by the death certificate. Stratification of socioeconomic status was done by income as low (lower 30th percentile), high (higher 30th percentile) and middle, which was reclassified annually. Shift in socioeconomic status was defined as any change in the income class from baseline. Results During the follow-up of a median 10 years, cardiovascular mortality was significantly higher among middle and low socioeconomic status groups (hazard ratio and 95% confidence interval for middle 1.92 (1.68–2.19) and low 1.73 (1.50–2.00)) compared to the high socioeconomic status group after adjustment for age, gender, residence, blood pressure, fasting glucose, smoking and medications (statins and antiplatelet agents). In the same regression model, an upward shift of socioeconomic status was associated with a lower risk of cardiovascular death (hazard ratio 0.46, 95% confidence interval 0.40–0.52), while a downward shift was not a significant predictor. Conclusion An upward shift of socioeconomic status was associated with a lower risk of cardiovascular mortality after adjustment for baseline socioeconomic status, conventional risk factors and risk-reducing pharmacological treatments.